When I want to store DateTime it stored like:

bsonWriter.WriteString(dateTime.ToString("yyyy-MM-ddTHH:mm:ss.FFFFFFFK"));

Problem:
Now I want to query my DateTime property by Eq query. Query Serializer generate something like: "Property":ISODate("2012-04-13T06:00:00Z")

And I got empty result set, because dates doesn't match - date in base with milliseconds, generated date - without

I can do only workaround about this:
"DateTimeProperty" :

{ "$gte" : ISODate("2012-04-13T06:00:00Z"), "$lt" : ISODate("2012-04-13T06:00:01Z") }

Like "query Date" <= DateTime < "query Date" + 1 seconds (to handle milliseconds)